Scotsman MVP456 Service Manual page 23

Page 23
DIAGNOSIS
Problem
Shut down on maximum
harvest time
Shut down on minimum
freeze time
Long freeze cycle
Long Harvest Cycle
False bin full signal
Fan blade vibrates
Compressor vibrates
Water pump vibrates
Panels vibrate
Likely Cause
Ice bridge thickness too small,
not enough ice to open curtain
Ice bridge thickness too large,
ice frozen to evaporator frame
Purge valve does not open, water
melts ice bridge, not enough ice to
open curtain
Incomplete ice formation
Curtain out of position
Curtain switch does not open when
curtain does
Machine in very cold ambient
Hot gas valve does not open
Harvest assist probe out of position -
ejector pin not retracted
Damaged evaporator
Fan motor stays on during harvest
Grounded ice thickness sensor
Dirty air filters
Dirty condenser
Hot ambient
Water leak
Water inlet valve leaks through
Low on refrigerant
Incorrect superheat
Fan(s) cycle on and off
Dirty evaporator
No harvest assist
Bridge thickness too big
Machine in very cool ambient
Ice jammed in between curtain and sump
Curtain does not close correctly
Blade is bent
Fan motor mount is broken
Mounting bolts loose
Pump bearings worn
Mounting screws loose
Probable Solution
Check and adjust if needed
Check and adjust if needed
Check purge valve
Check water distributor for partially
plugged holes
Check curtain for swing restriction
Check switch with ohmmeter
Move machine to a warmer location
Check hot gas valve, check controller
using test mode
Check harvest assist mechanism -
spring should retract pin
Check evaporator surface
Check controller using test mode
Check sensor for dirt and position.
Clean and check gap to evaporator surface.
Clean filters
Clean condenser
Reduce room air temperature
Check purge valve, check curtain
Check inlet valve
Add refrigerant, if cycle time drops,
check for leak
Check evaporator superheat, if
significantly low or high, replace TXV
Check pressures fans cycle at.
Replace fan pressure switch if too low
De-scale water system
Check harvest assist solenoid
Check and adjust bridge thickness
Increase room temperature
Clear ice away
Check curtain for proper swing
Replace fan blade
Replace motor mount
Tighten bolts
Replace pump
Tighten screws
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